| (_l1, t1) <- coercionKind co2
-- e |> (g1 :: S1~L) |> (g2 :: L~T1)
-- ==>
- -- e, if T1=T2
- -- e |> (g1 . g2 :: T1~T2) otherwise
+ -- e, if S1=T1
+ -- e |> (g1 . g2 :: S1~T1) otherwise
--
-- For example, in the initial form of a worker
-- we may find (coerce T (coerce S (\x.e))) y